Some internal combustion engines include an adjustable or slideable camshaft assembly. The camshaft assembly includes a base camshaft that is rotatable about a cam axis. A lobe pack is slideably attached to the camshaft for axial movement along the cam axis relative to the camshaft. The lobe pack is rotatable with the camshaft about the cam axis. The lobe pack is moveable between at least two different axial positions along the cam axis. Each different position of the lobe pack presents a different cam lobe having a different lobe profile for engaging a respective valve stem of the engine. Accordingly, by adjusting the position of the lobe pack, the cam profile that each valve stem of the engine follows may be changed.
The lobe pack includes a barrel cam that defines a control groove disposed annularly about the cam axis. A first shifting pin is moveable along a first pin axis in a direction transverse to the cam axis. The first shifting pin moves between an engaged position and a disengaged position. When disposed in the engaged position, the first shifting pin is engaged with the control groove, such that interaction between the first shifting pin and the control groove moves the lobe pack axially along the cam axis relative to the camshaft, in a first axial direction and into a first axial position, as the lobe pack rotates about the cam axis with the camshaft. A second shifting pin is moveable along a second pin axis in a direction transverse to the cam axis. The second shifting pin moves between an engaged position and a disengaged position. When disposed in the engaged position, the second shifting pin is engaged with the control groove, such that interaction between the second shifting pin and the control groove moves the lobe pack axially along the cam axis relative to the camshaft, in a second axial direction and into a second axial position, as the lobe pack rotates about the cam axis with the camshaft. When disposed in their respective disengaged positions, the first shifting pin and the second shifting pin are disengaged from the control groove such that the lobe pack remains positionally fixed along the cam axis, relative to the camshaft, as the lobe pack rotates about the cam axis with the camshaft. The lobe pack remains positionally fixed relative to the camshaft via an interlocking detent ball and detent groove retention mechanism disposed on the lobe pack and the camshaft respectively.
During normal operation, the camshaft and the lobe pack only rotate about the cam axis in a first rotational direction. The control groove is shaped to engage the first shifting pin and the second shifting pin, to guide the lobe pack between the first axial position and the second axial position along the cam axis respectively, when the camshaft and the lobe pack are rotating in the first rotational direction.